Nonlinear energy sink and use of same in sound insulation

The present invention relates to a building element comprising a sheet (11) of a rigid material and at least one nonlinear energy sink (9) comprising - a blade (1) with two end parts (2a) and a nonlinear spring function intermediate part (2b), - a mass (3) fixed to the nonlinear spring function intermediate part (2b) of the blade, - a fixing means (4) allowing the two end parts (2a) of the blade (1) to be fixed to a solid support in such a way that the nonlinear spring function intermediate pat (2b) can oscillate about its position of equilibrium or its positions of equilibrium, the nonlinear energy sink (9) being fixed rigidly to the sheet (11) by the fixing means (4). It also relates to a partition wall containing such a building element and to the use of such an energy sink or building element for reducing the acoustic transparency of a wall.